templatekw: force noprefix=False to insure diffstat consistency (issue4755)

The result of diffstatdata should not depend on having noprefix set or not, as
was reported in issue 4755. Forcing noprefix to false on call makes sure the
parser receives the diff in the correct format and returns the proper result.

Another way to fix this would have been to change the regular expressions in
path.diffstatdata(), but that would have introduced many unecessary special
cases.

mercurial/templatekw.py

@@ -299,7 +299,7 b' def showdiffstat(repo, ctx, templ, **arg'
     """String. Statistics of changes with the following format:
     "modified files: +added/-removed lines"
     """
-    stats = patch.diffstatdata(util.iterlines(ctx.diff()))
+    stats = patch.diffstatdata(util.iterlines(ctx.diff(noprefix=False)))
     maxname, maxtotal, adds, removes, binary = patch.diffstatsum(stats)
     return '%s: +%s/-%s' % (len(stats), adds, removes)
 

tests/test-import.t

@@ -1517,6 +1517,13 b' prepare a stack of patches depending on '
   |
   o  initial [Babar] 2: +8/-0
   
+Adding those config options should not change the output of diffstat. Bugfix #4755.
+
+  $ hg log -r . --template '{diffstat}\n'
+  1: +1/-0
+  $ hg log -r . --template '{diffstat}\n' --config diff.git=1 \
+  >   --config diff.noprefix=1
+  1: +1/-0
 
 Importing with some success and some errors: